Growth and phase separation behavior in Ge-doped Sb-Te thin films deposited by combined plasma-enhanced chemical vapor and atomic layer depositions

The growth, phase separation, crystallization behavior, and electrical properties of various Ge-doped Sb-Te thin films were examined. The films were deposited by combined plasma-enhanced chemical vapor and atomic layer depositions at a wafer temperature of 150 °C using Ge(i-C₄H ₉)₄, Sb(i-C₃H₇)₃, and Te(i-C₃H₇)₂ as the precursors for Ge, Sb, and Te, respectively. The different compositions were obtained by adjusting the Ge and Sb precursor injection times. Segregated crystalline Sb islands were observed in amorphous Sb-rich Sb-Te thin films containing over 10 atom % of Ge. The crystallization kinetics of the Ge-doped SbTe alloys, which depends on the concentration ratio of Sb/Te and the bond energy between Ge, Sb, and Te, provide clues to help understand the phase separation behavior of the films at growth temperature. Ge₁₇Sb₅₈Te₂₅ and Ge ₃₁Sb₃₈Te₃₁ showed the highest resistivity of 67 Ω cm at the as-deposited state and exhibited a crystallization temperature of ∼260 °C.